The present invention relates to an image recorder selectively operable with a plurality of toner cartridges each storing toner, or developer, having a different characteristic. More particularly, the present invention is concerned with an electrophotographic copier capable of automatically setting up optimum copy process conditions in association with the characteristic of toner to be used.
Generally, an electrophotographic copier is designed to meet a particular requirement depending upon the application, e.g. compact configuration, high-speed operation, cut-down of cost or that of power consumption. It is a common practice to implement such a particular requirement by a particular kind of copying process. Concerning a developing process, two different processes are available: a process using a one-component developer which is constituted by toner only and a process using a two-component developer made up of toner and carrier. These developing processes are also selectively adopted to satisfy any of the above requirements. For example, toner applicable to the developing process which uses a two-component developer include lusterless toner, low melting point toner, oilless toner and other special toners, and each is used with a particular copying process. The lusterless toner, for example, consists of carbon and styrol or similar resin the mixture ratio and particle sizes of which are variable to make the surface of toner appear irregular after fixation (so-called aventurine), as well known in the art. The low melting point toner is produced by replacing the whole or part of the resin to be mixed with carbon with resin having a low melting point and adopted for an application wherein power saving is the primary consideration. Further, the oilless toner is implemented by resin which is the mixture of styrol resin and polypropyrene resin or the like and eliminates the need for silicon oil or similar composition which is usually applied to a fixing roller to facilitate the separation of a paper sheet from the fixing roller.
Copy process conditions for achieving desirable copies depend upon the characteristic of toner to be used. Customarily, once a particular kind of toner is selected in relation to a desired application, copy process conditions which match with the kind of toner are fixedly set up and, therefore, a single copier is not selectively operable with different kinds of toner. Hence, a copier once purchased cannot adapt itself to a different object and condition of use which may be desired afterwards, unless the copier is replaced with another type of copier. While various efforts have heretofore been made to render a single copier operable with toner of different colors and different characteristics, all of them require a developing unit or a process cartridge which includes a discharger and a developing unit to be replaced with another depending upon the kind of toner used. It is therefore necessary to furnish a single copier with different kinds of replaceable developing units or process cartridges. This not only increases the burden cast upon the user but also makes the storage and disposal of the process cartrdiges troublesome.
Furthermore, a prior condition with a conventional toner cartridge is that the same kind of toner be supplied and not that the kind of supplied toner be detected to select and change the copy process conditions in association therewith. Various kinds of toner have recently been developed which may be used in a mixture each by a small amount despite their different characteristics, i.e., which may be mixed in a transitional stage which occurs after toner replacement. In any case, however, optimum process conditions which match with the individual toner are different from each other. With the prior art copier, therefore, when a toner cartridge storing a certain kind of toner is simply replaced with toner cartridge storing a different kind of toner, copying operations cannot be performed except under the same process conditions as the previous toner.